1. Field of the Invention
The present invention generally relates to a control system in a vehicle. Particularly, the present invention relates to control for a vehicle including at least a pair of driving power transmission members engaged with each other with a slack on a driving power transmission path through which a driving power is transmitted from a driving power source to a drive wheel.
2. Description of the Related Art
A vehicle such as a motorcycle includes various driving power transmission members such as gears, a dog clutch, a chain, sprockets, and splines on a driving power transmission path from an engine (driving power source) to a drive wheel. These driving power transmission members are arranged such that adjacent driving power transmission members are engaged with each other with a slack on the driving power transmission path. Because of this, when a rotational speed difference is generated between the driving power transmission member located at an upstream side of the engaged portions and the driving power transmission member located at a downstream side of the engaged portions on the driving power transmission path, due to an increase or decrease in an engine speed, an engine braking operation, or the like, these driving power transmission members are disengaged (move away) from each other for a moment (temporarily) and contact each other again thereafter.
For example, during accelerated driving of the vehicle, an increasing engine driving power is transmitted in a state where a surface of the driving transmission member located at the upstream side, which surface is located at one side in a rotational direction, contacts and presses a surface of the driving transmission member located at the downstream side, which surface is located at an opposite side in the rotational direction. Under this condition, if the vehicle shifts to a deceleration state, the upstream driving power transmission member is displaced relative to the downstream driving power transmission member toward the opposite side in the rotational direction and away from each other for a moment and then a surface of the upstream driving transmission member, which surface is located at the opposite side in the rotational direction, re-contacts a surface of the downstream driving transmission member, which surface is located at one side in the rotational direction. At this time, if the relative speed difference between the driving power transmission members is great, they collide against each other and an impact is generated and transmitted to the driver, which makes the driver's driving feeling worse.
To solve this, a technique has been proposed, in which an input shaft located at an upstream side on the driving power transmission path and/or an output shaft located at a downstream side on the driving power transmission path are accelerated or decelerated based on a relative rotational position and/or a relative rotational speed (rotational speed difference) of the input shaft and the output shaft (e.g., see Japanese Laid-Open Patent Application Publication No. 2005-321088). According to this technique, the impact generated by the re-contact between the driving power transmission members at engaged portions engaged with each other with a slack can be mitigated in such a manner that the relative speed difference between the driving power transmission members is lessened before they re-contact each other after they move away from each other.
In the above prior art example, it is necessary to detect the rotational speed of the input shaft located at the upstream side of the engaged portions and the rotational speed of the output shaft located at the downstream side of the engaged portions. For example, Japanese Laid-Open Patent Application Publication No. 2005-321088 discloses that an input shaft sensor 401 is attached on a main shaft 204 which is an input shaft of a transmission 203 and an output shaft sensor 402 is attached on a drive shaft 211 which is an output shaft of the transmission 203.
However, in a case where a sensor is attached on an output shaft of a transmission in, for example, a motorcycle, it is necessary to prevent an adverse effect which would be caused by clattering of a drive chain installed around a sprocket present in the vicinity of the sensor. To avoid misdetection which would be caused by the clattering or vibration of the chain, it is necessary to support the sensor in a floating state by a damper, or to cover the sensor with a stiff metal-made cover member in order to avoid contact with the clattering or vibrating chain, which would increase a cost.